Introduction
Unique keys in SQL are like secret codes that make sure every piece of information in a database is one-of-a-kind. Imagine you're in a room full of people where everyone must wear a unique badge. Just like those badges, unique keys help tell each piece of data apart from the others, ensuring no two pieces are exactly the same.
In this article, we're going to explore how these special keys work & why they're so important in organizing & maintaining data efficiently. We'll walk through how to set them up when creating new tables, how to add them to existing ones, & even how to remove them if we need to. Let's get started & unlock the power of unique keys in SQL!
SQL UNIQUE Constraint on CREATE TABLE
When we create a new table in a database, it's like setting up a new room where each item needs its own special spot. The UNIQUE constraint in SQL is like telling the database, "Hey, make sure every item in this spot is different from the others!" This keeps our data tidy & easy to find.
Let's say we're making a list of all the students in a class, & we want to make sure each student's ID number is different so there's no mix-up. Here's how we can do it:
In this example, StudentID is our unique key. This means no two students can have the same ID number. It's like giving each student a unique badge number. This way, when we look for a student in our list, we're sure to find just the one we're looking for, with no duplicates causing confusion.
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